1. Technical Field
This invention relates to novel apparatus and process for continuous or on-line ozonation in ultra pure water membrane filtration. In one aspect, the invention relates to a separations process for continuous or on-line ozonation in providing particle-free ultra pure water by membrane filtration for use in the electronics and semiconductor industries.
2. Background
High purity water is required for semiconductor device manufacturing. In semiconductor manufacturing, high purity water is used primarily for wafer rinsing. This rinsing process removes both contaminants inadvertently introduced to the wafer during the manufacturing process as well as chemicals intentionally introduced to the wafer for the purpose either of cleaning or of etching patterns into the semiconductor surface or the conductive or dielectric thin films grown or deposited on this surface as required to produce a semiconductor device.
These cleaning or etching chemicals include, but are not limited to ammonium fluoride, piranha solutions (the generic name used for mixtures of sulfuric acid and a strong oxidizer: usually hydrogen peroxide or ozone), and the two component solutions comprising the industry standard RCA cleaning method, i.e., the so-called SC-1 and SC-2 solutions. (W. Kern and D. A. Puotinen, RCA Review, Volume 31, pp. 187, 1970.) SC-1 is a mixture of ammonium hydroxide, unstabilized hydrogen peroxide, and ultra pure water. SC-2 is a mixture of hydrochloric acid, unstabilized hydrogen peroxide, and ultra pure water.
Ultra pure water rinses are also used to remove the solvents used for the removal of photoresists.
Ultra pure water is the chemical used in the greatest quantity in semiconductor manufacturing, and extremely large quantities of ultra pure water are produced in modern semiconductor production facilities.
The greatest cause of yield loss in modern semiconductor manufacturing is particulate contamination. Particles interrupt the photolithographic patterns that define integrated circuit components and can cause open circuits in the conductive metal thin films that wire these circuits together. When attached to a semiconductor wafer, particles are extremely difficult to remove as they electrostatically bond to the wafer. Therefore, all of the fluids which contact the semiconductor wafer must be rigorously filtered to remove particles. This includes ultra pure water.
Conventional processes for producing ultra pure water typically use dead-end filtration with polymeric membranes. For example, conventional ultrafilters (similar in design to RO membrane systems) are used to produce high purity water for electronics applications. Spiral wound membranes, another commonly employed technology, require low solids in the feed stream and have high pressure drops associated with the restrictive liquid flow paths through their extremely narrow channels. The fouling of polymeric ultrafilters is a problem as is the requirement to periodically clean these filters off line. (D. Sinha, "Pretreatment Process Considerations for the Semiconductor Industry", Ultrapure Water 7(6), pp. 21-30 (1990).)
These and other known processes for producing ultra pure water for the electronics or semiconductor manufacturing applications are represented in the following.
U.S. Pat. No. 5,292,439, assigned to Mitsubishi Kasei of Japan, discloses a method for preparing ultra pure water for use in electronics industries. The patent discloses that the water quality of ultra pure water is largely affected by impurities eluted from the materials constituting the purification apparatus. (Col. 1, bottom). An improved ion exchange process is provided to overcome the problems of the impurities eluted from the materials constituting the purification apparatus.
U.S. Pat. No. 5,259,972, assigned to Nippon Rensui and Mitsubishi Denki of Japan, discloses apparatus and method for purifying water for use in the electronics industry. The patent discloses that it is known to combine an ultrafilter membrane with ion exchange, ultraviolet (UV) sterilizers, cartridge filters, reverse osmosis (RO) and other components to produce ultra pure water. (Col. 1, line 18).
U.S. Pat. No. 5,160,429, assigned to Tadahiro Ohmi of Japan, discloses supplying ultra pure water for the electronic industry. The patent shows the use of ultrafiltration units 108 and 109.
U.S. Pat. No. 5,128,043 discloses apparatus and method for purifying water for use in the electronic industry. The patent discloses using an electric field. A specific object is to remove particles. Another object is to provide a method and apparatus not affected by ozone. A membrane filter 4 removes particulates. A final filter 12 is sized at 0.2 microns.
U.S. Pat. No. 5,124,033, assigned to Shinko Pantec of Japan, discloses an ultra pure water producing system for the semiconductor manufacturing process. Metallic ions and particulates are removed. An ultrafilter 39 is disclosed. The patent discloses that when water comes in contact with the materials of the devices and pipings, materials such as silica are leached out.
U.S. Pat. No. 5,073,268, assigned to Ebara Corp. of Japan, discloses a process for purifying water or ultra pure water for use in the electronics industry. An ultrafilter unit 22 is disclosed.
U.S. Pat. No. 5,061,374, assigned to Micron Technology of Boise, Id., discloses an ultra pure water system employing a second train which reduces particulate in the manufacture of integrated chips (IC's). The patent discloses ozone and membrane filters and reduces particulate in the water to a level of less than 30 counts per milliliter sizes 0.1 micron to 1 micron. (Col. 1, lines 48-50.)
U.S. Pat. No. 5,024,766 discloses water purification which reduces particulate in semiconductor manufacturing. The patent discloses ozone and submicron filter 20. Polymeric membrane filters marketed as Fluorodyne are disclosed at the top of Col. 9.
U.S. Pat. No. 4,879,041, assigned to Hitachi of Japan, discloses a process for producing ultra pure water for semiconductor manufacturing. The patent discloses ozone and membrane filters.
U.S. Pat. No. 4,863,608, assigned to Nomura Micro Science of Japan, discloses a process for producing ultra pure water for integrated circuits manufacturing. The patent discloses ultrafiltration and microfiltration.